1. Field of the Invention
This invention relates to a color laser system that can be utilized for laser projection of television, video pictures, computer generated pictures or other information on small or large screens. In particular, the invention relates to the type of lasers used in the system.
2. Description of the Prior Art
Shortly after the demonstration of the laser in 1960, there were several demonstrations of projection of video images using laser systems. Descriptions of these laser displays can be found in the following references:
1. Baker, Charles E., IEEE Spectrum p 39 (1968), "Laser Display Technology". PA0 2. Koppel, A. et al, Applied Optics p 1667 (1966), "A Television Display using Acoustic Deflection and Modulation of Coherent Light". PA0 3. Stavis, G., U.S. Pat. No. 3,507,984, Apr. 21, 1970, "Laser Multicolor Television Display Apparatus". PA0 4. Korpel, A., U.S. Pat. No. 3,524,011, Aug. 11, 1990, "Laser Color Display Utilizing Acoustical Light Modulators". PA0 5. Baker, C. E., U.S. Pat. No. 4,549,800, Dec. 22, 1970, "Laser Display". PA0 6. Pinnow, D. A. and Van Ultert, Le Grand G., U.S. Pat. No. 3,691,482 Sep. 12, 1972, "Display System". PA0 7. Yamamoto, M., U.S. Pat. No. 3,818,129, Jun. 18, 1974, "Laser Imaging Device". PA0 8. Driskell, C., U.S. Pat. No. 3,992,718, Nov. 16, 1976, "Color Panoramic Laser Projector". PA0 9. Spooner, A. M., and Lobb, D. R., U.S. Pat. No. 414,572, Mar. 20, 1979, "Laser Elimination of Mode Beating". PA0 10. Whitby, C. M., U.S. Pat. No. 4,297,723, Oct. 27, 1981, "Wide Angle Laser Display System". PA0 11. Shortle, M. C., and Lobb, D. R., U.S. Pat. No. 4,613,201, Sep. 23, 1986, "Light Projection Apparatus". PA0 12. Crowley, R. P., U.S. Pat. No. 4,720,747, Jan. 19, 1988, "Sequential Plane Projection By Laser Video Projector". PA0 13. Kobayashi, K., U.S. Pat. No. 4,833,528, May 23, 1989, "Color Video Projecting Apparatus Using Acousto-Optical Deflector". PA0 14. Crowley, R. P., U.S. Pat. No. 4,851,918, Jul. 25, 1989, "Sequential Plane Projection By Laser Video Projector". PA0 15. Yang, K. Y., U.S. Pat. No. 4,978,202, Dec. 18, 1980, "Laser Scanning System for Displaying Three-Dimensional Color Image". PA0 16. Linden, P. A., and Pease, R. W., U.S. Pat. No. 5,136,426, Aug. 04, 1992, "Laser Projection Apparatus".
Various laser display systems and devices are described in the following U.S. Patents:
The foregoing patents and papers demonstrate that high definition full color television projection of images can be accomplished using laser based systems. In particular, the use of modulators, scan systems and associated electronics have been fairly well developed. However, these laser systems have significant limitations, a primary limitation being the lack of availability of the lasers in a suitable small efficient form.
Requirements on the laser sources are as follows for a full color system:
a) A red laser with a proximate wavelength of 610 to 640 nm. PA1 b) A green laser with a proximate wavelength of 510 to 540 nm. PA1 c) A blue laser with a proximate wavelength of 460 to 480 nm.
These particular wavelengths are required in order to achieve full color in the projection of color images. Additional requirements are that the lasers produce at least a fraction (1/10) of a watt so that a suitable luminosity or brightness can be produced. Ideally, the lasers should be small, efficient and inexpensive. Most designs use continuous wave (CW) lasers to simplify the timing.
Several different lasers have been utilized, the most common choice being an Argon ion laser for the blue and green components, and a Krypton or He Ne or Argon pumped dye laser for the red light. Other possible lasers include the He Cd laser and a pulsed copper vapor laser.
The major problem with the forementioned lasers is that they have a very low electrical input to light conversion efficiency, typically less than 0.1%. This means that they require large amounts of electrical power input to the system (typically more than 10 Kw) and also the removal of large heat loads, usually by water cooling. The laser systems also, as a result, tend to be relatively large. Thus their use is generally limited to applications suitable for large, immobile and expensive equipment. It would therefore be desirable to provide a laser projection system which uses lasers that are efficient, small in size and relatively inexpensive, permitting the laser system to be used for a host of applications where small size is a paramount requirement.